C02-Wireless_Transmission - Mobile Communications Chapter...

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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.1 Mobile Communications Chapter 2: Wireless Transmission ± Frequencies ± Signals ± Antenna ± Signal propagation ± Multiplexing ± Spread spectrum ± Modulation ± Cellular systems
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.2 Frequencies for communication coax cable VLF = Very Low Frequency UHF = Ultra High Frequency LF = Low Frequency SHF = Super High Frequency MF = Medium Frequency EHF = Extra High Frequency HF = High Frequency UV = Ultraviolet Light VHF = Very High Frequency Frequency and wave length: λ = c/f wave length λ , speed of light c 3x10 8 m/s, frequency f 1 Mm 300 Hz 10 km 30 kHz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100 µ m 3 THz 1 µ m 300 THz visible light optical transmission twisted pair VLF LF MF HF VHF UHF SHF EHF infrared UV
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.3 Frequencies for mobile communication ± VHF-/UHF-ranges for mobile radio ± simple, small antenna for cars ± deterministic propagation characteristics, reliable connections ± SHF and higher for directed radio links, satellite communication ± small antenna, beam forming ± large bandwidth available ± Wireless LANs use frequencies in UHF to SHF range ± some systems planned up to EHF ± limitations due to absorption by water and oxygen molecules (resonance frequencies) z weather dependent fading, signal loss caused by heavy rainfall etc.
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.4 Frequencies and regulations ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences) Europe USA Japan Cellular Phones GSM 450-457, 479- 486/460-467,489- 496, 890-915/935- 960, 1710-1785/1805- 1880 UMTS (FDD) 1920- 1980, 2110-2190 (TDD) 1900- 1920, 2020-2025 AMPS , TDMA CDMA 824-849, 869-894 1850-1910, 1930-1990 PDC 810-826, 940-956, 1429-1465, 1477-1513 Cordless CT1+ 885-887, 930- 932 CT2 864-868 DECT 1880-1900 PACS 1850-1910, 1930- 1990 PACS-UB 1910-1930 PHS 1895-1918 JCT 254-380 Wireless LANs IEEE 802.11 2400-2483 HIPERLAN 2 5150-5350, 5470- 5725 902-928 5150-5350, 5725-5825 IEEE 802.11 2471-2497 5150-5250 Others RF-Control 27, 128, 418, 433, 868 315, 915 RF-Control 426, 868
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.5 Signals I ± physical representation of data ± function of time and location ± signal parameters: parameters representing the value of data ± classification ± continuous time/discrete time ± continuous values/discrete values ± analog signal = continuous time and continuous values ± digital signal = discrete time and discrete values ± signal parameters of periodic signals: period T, frequency f=1/T, amplitude A, phase shift ϕ ± sine wave as special periodic signal for a carrier: s(t) = A t sin(2 π f t t + ϕ t )
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.6 Fourier representation of periodic signals ) 2 cos( ) 2 sin( 2 1 ) ( 1 1 nft b nft a c t g n n n n π = = + + = 1 1 0 0 tt ideal periodic signal real composition (based on harmonics)
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 2.7 Signals II ± Different representations of signals ± amplitude (amplitude domain) ± frequency spectrum (frequency domain) ± phase state diagram (amplitude M and phase ϕ
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This note was uploaded on 02/28/2008 for the course CSCI 6360 taught by Professor Wu during the Spring '08 term at University of Texas at Dallas, Richardson.

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C02-Wireless_Transmission - Mobile Communications Chapter...

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